Instantaneous fringe-order identification using dual broadband sources with widely spaced wavelengths

A new fringe-order identification technique for interferometric optical fibre sensors is described using dual broadband optical sources coupled with white-light interferometry. Compared with previous work, this technique enables the central (zero-order) fringe to be directly identified through its dominant amplitude, and does not require digitisation and its associated computing power. Therefore, it is suitable for coherence multiplexed quasidistributed sensors and for monitoring quickly varying measurands.